By Mary Anne Bishop
In 2008 the Science Center installed an underwater array of acoustic receivers across the mouth of Port Gravina in Prince William Sound to “listen” for acoustic-tagged fish. These arrays detected tagged subadult lingcod dispersing out of Port Gravina and detected short trips in and out of Port Gravina made by older, adult lingcod. In 2011, an elephant seal equipped with a special tag designed to detect other tags recorded a lingcod near Yakutat, one year after it left Port Gravina! That discovery was exciting because it was the first evidence of population connectivity between lingcod in Prince William Sound and lingcod in the Gulf of Alaska.
Six new arrays across the major entrances and passages to Prince William Sound have now radically changed our ability to determine population connectivity between fish populations in the Sound and the Gulf of Alaska. The Prince William Sound array is the first of its kind in Alaska and is part of a larger global network of acoustic receivers and oceanographic monitoring equipment designed to identify on small to large scales the critical habitats and migration pathways of aquatic animals important to humans.
The first research project to take advantage of the arrays is investigating seasonal movements of Pacific herring. While the general areas of where herring spawn in Prince William Sound is somewhat predictable, less is known about where herring go after spawning. Do they stay in Prince William Sound or go out into the Gulf of Alaska to forage during the summer months? In early April 2013 we tagged 69 adult herring right before they spawned. By fall 2013 we should know whether or not any of our acoustically tagged Pacific herring leave and subsequently return to the Sound, giving new insight into large-scale seasonal movements.
The herring movement study is being sponsored by the Exxon Valdez Oil Spill Trustee Council as part of the larger, long-term Herring Research and Monitoring Program while the acoustic array is being sponsored by Canada’s Ocean Tracking Network in collaboration with the Prince William Sound Science Center.